// 4. 具体同事：用户
public class User : Colleague
{
  public User(IMediator mediator, string name) : base(mediator, name) { }

  public override void Receive(string message, Colleague sender)
  {
    base.Receive(message, sender);
    // 可以在这里添加个性化处理，如过滤、提醒等
  }
}